Cleaning processes play a particularly important role in the reconditioning of synthetic materials.
In the chemical industry, synthetic materials are initially produced in the form of powders and are then converted into granules to facilitate handling. These granules are placed on the market and are processed by the manufacturers of articles made of synthetic materials. The molten granules are shaped into tubes, foils and the like with the aid of extruders.
Since the granular materials produced by the chemical industry are relatively clean, there is generally no need for special cleaning prior to extrusion. However, if a very high degree of purity is required in the finished products, screens are inserted, even in the case of granules used for the first time, in order to eliminate possible impurities.
Cleaning synthetic raw materials is usually desirable when materials already used are to be reconditioned. Used synthetic foils, synthetic tubes and other objects made of synthetic materials, which are subjected to a so-called recycling process, must therefore usually be cleaned.
A cleaning process of this kind may consist, for example, in washing the articles, drying them, and passing them to a melting unit with a cleaning screen. The molten masses of synthetic materials are pressed through the cleaning screen which retains the impurities. After a certain length of time, the screen is soiled to such an extent that it must be replaced.